They say monsters are born in darkness, but nobody asks what happens when darkness is born inside a human. Twenty-one-year-old Alvina Hill is running out of time. Drowning in medical debt and desperate to save her dying mother, she gambles everything on a reckless proposition: offering herself as a contract girlfriend to the coldest man in Los Angeles—trillionaire CEO Lucian Moon. Lucian is a 500-year-old hybrid alpha whose inner demon has been dead to the world for centuries. He doesn't do love, and he definitely doesn't do curvy women. But when his immortal mother, Maria, who pesters him about finding a new mate, suddenly visits town, Lucian is forced to activate Alvina's contract. To trick the spies, his mother sent to spy on them, he initiates a 20-Day Human Experience Plan, taking his innocent fake girlfriend to do all the ordinary things she's missed out on while caring for her mother. But the moment their lips touch, his dormant monster violently awakens, craving her soul. When a blood-soaked betrayal shatters Alvina's trust, she flees. Driven to absolute madness, Lucian declares her missing on every single billboard across the globe, launching a five-billion-dollar international hunt for his runaway mate. When ancient witch kingdoms and deadly family secrets collide, will Alvina choose to step into his hell willingly?